1. Field of the Invention
The present invention relates to the field of computer tomography, and more particularly to tomographic reconstruction and volume rendering using texture mapping.
2. Related Art
Volume visualization of real-time or recorded images encompasses not only viewing, but also construction of a volumetric data set from the more basic projection data obtained from sensor sources. Most volumes used in rendering are derived from such sensor data. A primary example being Computer Aided Tomographic (CAT) x-ray data. This data is usually a series of two dimensional projections of a three dimensional volume. The process of converting this projection data back into a volume is called tomographic reconstruction. The term tomographic reconstruction or Computed Tomography (CT) is used to differentiate it from signal reconstruction: the rebuilding of a continuous function (signal) from a discrete sampling of that function. See, Russ, J., The Image processing Handbook, CRC Press (1992), pp. 339-365; Kak, A. and Slaney, M., Principles of Computerized Tomographic Imaging, IEEE Press (1988), pp. 1-4; Bracewell, R., Two-Dimensional Imaging, Prentice-Hall (1995), pp. 505-538; and Jain, A., Fundamentals of Digital Image Processing, Prentice-Hall (1989), pp. 431-475.
Once a volume is tomographically reconstructed it can be visualized using volume rendering techniques. (See, Kajiya, J. and Von Herzen, B., "Ray Tracing Volume Densities," Computer Graphics, Vol. 18, No. 3, July 1984, pp. 165-174; Sabella, P., "A Rendering Algorithm for Visualizing 3D Scalar Fields," Computer Graphics, Vol. 22, No. 4, August 1988, pp. 51-58; Upson, C. and Keeler, M., "V-BUFFER: Visible Volume Rendering," Computer Graphics, Vol. 22, No. 4, August 1988, pp. 59-64; Drebin, B. et al., "Volume Rendering," Computer Graphics, Vol. 22, No. 4, August 1988, pp. 65-74; Westover, L., "Footprint Evaluation for Volume Rendering," Computer Graphics Vol. 24, No. 4, August 1990, pp. 367-376; Krueger, W., "The Application of Transport Theory to the Visualization of 3-D Scalar Fields," Computers in Physics, April 1991, pp. 397-406; and Totsuka, T. and Levoy, M., "Frequency Domain Volume Rendering," Computer Graphics , August 1993, pp. 271-278.)
The operations of tomographic reconstruction and volume rendering have traditionally been decoupled, being handled by two separate algorithms. Both operations have been commercially implemented by specialized, very expensive CT systems. Medical procedures that require this hardware are likewise expensive, thus limiting patients accessibility to such procedures. What is desired is a system and method for performing these operations in a more efficient, less costly manner.